This invention is directed to devices and equipment for removing process dust coming from a dust generating machine, such as a sanding machine, and separating the dust from exhaust air flowing from the machine. The invention is more specifically directed to a compact and efficient system for removing the production dust from the work area to a dust collection station located beyond the work area, and which removes a majority of the air from the dust flow.
For many types of machines for processing a workpiece, some means has to be provided to dispense with the grindings, chips, and particulate matter that is generated by the machine during operation. For example, in the case of wood working machines, such as sanders, joiners, and the like, wood that is removed from a workpiece has to be collected and removed from the work area so as to avoid either a breathing hazard for the workman or a fire hazard. More specifically, in the case of portable equipment, such as floor sanders and edgers, it is conventional to draw off the dust that is generated by the machines and then send the air that is carrying the dust into a filter bag arrangement. An alternative technique is to attach a flexible hose or conduit to the dust outlet duct of the machine, and pump the air in the conduit, plus the entrained dust, to a collection station outside. For hand-held and mobile power tools, such as floor sanding equipment, the associated dust collection systems currently in use are cumbersome, impractical, or inadequate.
Two systems are currently in use. In one system, a blower on the machine is used to extract dust from the sanding or cutting operation, and the air and entrained dust go into a filter to collect the dust and filter the air. Work operations have to be suspended frequently to clean the filter and dispose of the collected dust. These maintenance-intense systems blind or clog readily, which reduces the pickup volume at the source, allowing the particulate waste to become airborne or to interfere with the operation. In the second system a flexible hose connects the unit to an external dust collection unit which draws the waste from the tool. These systems do not deliver the necessary air volume to the tool because of intrinsic mechanical problems of delivering air through the extended lengths of flexible tubing. Huge energy requirements and high air velocities are necessary to overcome frictional losses. Frictional losses in ducts increase exponentially with air velocity, so very wide diameter tubing is used, and this relatively large tubing, being quite cumbersome, hinders the operator in using the machine.
The system of long flexible hoses for collecting dust from portable wood sanding machines generally require a combination of a number of different hoses of various diameters, and a series of air pumps and blowers to maintain a satisfactory air draw. In addition, because all of the air that exits the sanding machine has to be carried all the way out to a remote collection station, the flexible hoses are required to have a rather large diameter.
A filter bag that is carried on the portable sanding machine is generally not satisfactory for a number of reasons. First, the bags are either too porous and do not remove enough particulates from the air, or are too fine and tend to clog after a period of operation, choking off the flow of exhaust air from the machine. Also, the bag collection system concentrates the fine particulates of a combustible material (wood dust), and this dust can ignite if a spark or heated material from the sanding operation lands in the bag. Such a situation can produce an explosion, and thus exposes the worker to an unnecessary danger.
A number of cyclonic separators have been proposed, typically for separating particulate matter, such as grain, powders, or dust, from a flow of air. However, to date, no one has proposed or considered mounting a cyclonic separator on a portable sander or other dust generating device so as to concentrate the dust and allow a smaller air flow, and a smaller conduit, to be used in moving the dust to the remote dust collection station.
Accordingly, it is an object of this invention to provide a highly energy efficient cyclonic separator-based dust collection system that avoids the drawbacks of the prior art.
It is a more specific object to provide a dust collection system in which the air pressure drop is dramatically reduced as compared with prior art dust collection systems.
It is a further object of this invention to provide a dust collection system in which a majority of the separation of dust from the exhaust air and the filtering of the exhaust air are carried out at the dust-generating machine or tool.
It is another object to provide dust collection system which reduces the power requirement, and also reduces the inherent fire or explosion hazard of the dust collection equipment.
According to an aspect of the invention, a compact and efficient dust collection system is provided for collecting production dust from a floor sander or other source machine that generates such dust in a production operation. The source machine has an internal blower for picking up the dust that the machine generates and exhausting the dust, entrained in a stream of air, to an exhaust outlet on the source machine. A compact, low-volume cyclonic separator is mounted on the source machine. The cyclonic separator has an inlet portion at the top, and an inner tubular baffle coaxial with the upper inlet portion and having open ends. The inlet portion and inner baffle define between them an annular inlet space. A frustoconic portion beneath the upper inlet portion and having a wide end joined at the inlet portion and this descends to a narrow lower end, where there is a dust outlet duct. An inlet duct receives the air flow and exhaust dust from the machine and injects this air flow into the annular inlet space. a pleated air filter, or equivalent air cleaning means, is situated above cyclonic separator for cleaning air that passes out through the tubular baffle. This permits the filtered clean air to return into the ambient air in the vicinity of the source machine. The dust is then concentrated at the bottom of the cyclonic separator. An elongated flexible duct or hose is coupled from the dust outlet duct of the cyclonic separator to a dust collection station positioned remote from said source machine. Because the dust is concentrated in the cyclonic separator, the air flow or volume required for conveying the dust to the dust collection station is reduced by a factor of between five and ten as compared with the systems discussed previously. This is because the secondary air flow between the separator and the dust collection station is used only for moving the preseparated dust, and does not have to supply the correspondingly greater air volume that is required to extract the waste dust from the cutting operation at the tool. Because the secondary air flow is reduced so greatly, a much smaller diameter hose can be used, typically xc2xe inch to 1 inch. This tubing can be bundled with the electric cord for the tool, and thus will not interfere with operation of the sander or other tool.
In a preferred embodiment, a rigid hollow conduit both serves as the tubing connecting the outlet of the machine to the cyclonic separator and as the means for supporting the cyclone separator on the machine.
The system can be run at a lower power requirement, e.g., at 110 volts, which is an advantage in that many non-commercial locations do not have 220 volts or three-phase power. The operator can continue to work without interruption, as the dust is carried to a much larger receptacle at the dust collection station. There is increased fire safety, as the heat and sparks that can result from the grinding or sanding operation are far from the dust storage location. An improved inlet port for the cyclonic separator permits superior dust pickup and better separation with less back pressure resulting from the separation. Industrial hygiene is vastly improved.
a second cyclonic separator can be used at the outside dust collection station, separating the dust from the incoming air flow, and dropping the dust from the nose of the cyclonic separator into a drum or similar receptacle.
The above and many other objects, features, and advantages of this invention will become apparent from the ensuing detailed description of the preferred embodiments, which is illustrated in the accompanying Drawing.